Indoor or hybrid electrical distribution substations may contain circuit breakers, disconnect panels, protection panels and other assets located at different locations. For example, these assets could be located on different floors or different parts of the same floor.
To ensure lineworker safety, switching orders include steps to verify that a circuit breaker in line with a target disconnect switch is open. These steps are carried out by inspecting circuit breaker indicators and ammeters at the protection panel. Lineworkers then verify the circuit breaker is open at the circuit breaker, where a visual indicator is integrated into the circuit breaker assembly. Finally, the remaining disconnect switches on the feeder are checked to verify they are in the appropriate state before the target switch is opened or closed.
When these assets are out-of-view from each other, such as when the assets are located on different floors or different parts of the same floor, it becomes challenging to execute switching orders. The main issue is not being able to monitor in real time the status of circuit breakers or other assets. In some instances, it is possible to inadvertently open a disconnect switch on a load, which could be hazardous and prone to developing dangerous and potentially fatal arc flashes. In fact, one such incident occurred at a substation in Massachusetts.
It is known to install current measurement devices on high voltage assets, or to use low voltage direct hard wiring between high voltage asset indicators and indicators installed, for example, at disconnect switch panels.